Seeing an oak treehopper (Platycotis vittata) was on my long-term wishlist, and it was so exhilarating to find one that I was on a nature high for a couple of days. These brightly-colored, odd-shaped true bugs look like they should live in tropical forests, but they’re fairly common in the Pacific Northwest.
Treehoppers are unique in lots of ways. But instead of talking about their parental care (unusual for insects) or symbiotic relationship with ants, I’m going to focus on their colors.
Oak treehoppers have four utterly different “looks,” and before the 1920’s people thought they were four different species. There are two color morphs and each of those can have either a pointy pronotum (the “shoulder” area that in this case grows to a thorn-like headtopper) or a rounded, more helmet-like pronotum.
Now imagine a color scheme that’s as different as possible from the pictures above. Maybe a darker background? Maybe yellow spots instead of stripes? Bingo. That’s what the other variation of Platycotis vittata looks like. No kidding. It’s phenomenal that natural selection settled on this as a winning strategy. The first source below has a picture of the darker patterned oak treehopper at the top of the page.
And it gets weirder. After going through five yet-different colorful stages (mainly black and red) as post-egg young nymphs, all oak treehopper adults start out in the striped pattern. Studies show the young ones are toxic to predators and often, insects that are poisonous are brightly colored. As they mature, some (maybe all?) of them transition to dark green-gray with yellow dots, and a few papers indicate the older ones aren’t distasteful to predators, but at that point, they blend in with the oak branches.
A few photos on iNaturalist show individuals that are a confused, messy combination of the two colorings. Not all older adults are the darker shade, however, as there are plenty of pictures of striped adult parents guarding over newly-hatched youngsters.
One more note: The oak treehopper’s “horn” is also poorly understood. A 1993 paper discusses how no one knows whether it’s defensive, a sensory organ, a camouflage device or none, or all, of the above.
Information page with references to the 1973 study: https://www.americaninsects.net/h/platycotis-vittata.html. Accessed 6/4/21.
1993 White paper by Thomas Wood: http://web.ntnu.edu.tw/~treehopper/lib/tkw_lib_pdf/wood_1993.pdf. Accessed 6/4/21.
iNaturalist photo of mixed striped and spotted oak treehopper: https://www.inaturalist.org/observations/80114192. Accessed 6/4/21.